<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>

<body>
  <div class="box">
    <section>section标签</section>
  </div>

  <script>
    let section = document.querySelector("section");
    let box = document.querySelector(".box");
    // section.innerHTML = "<h1>123</h1>";

    // section.innerHTML = section.innerHTML + "<h1>123</h1>";
    // section.innerText = "<h1>123</h1>";

    // console.log(box.innerText);
    // console.log(box.innerHTML);
    // console.log(box.outerHTML);



  </script>

</body>

</html>